Years ago before any "resto" parts were available, I used 1/8" Garlock or Durabla gasket material. Cut it to fit using what was left of the original as a pattern. been there nearly 40 years now with no issues.
Long time Mopar fan from Ontario. I have owned at least one of everything over the years. Still have my '69 Charger R/T. Looking at E bodies again.
Cheers